For electronics manufacturers focused on high-reliability production, ensuring absolute cleanliness of Printed Circuit Board Assemblies (PCBAs) is critical. A significant challenge arises when utilizing high-performance solder pastes such as KOKI S3X58-M500C. The flux residues left by this specific paste are notoriously difficult to remove. These residues tend to bake onto the surface and become deeply embedded underneath surface-mount components, resisting standard cleaning protocols.
To validate the integrity of their cleaning processes, quality assurance teams often resort to rigorously tearing components off the PCBAs to physically inspect the hidden areas. Recognizing this industry-wide pain point, DCT engineered a specialized protocol. By integrating the water-based Decotron® 411A cleaning fluid with advanced high-pressure Spray-In-Air systems, we developed a validated method capable of completely dissolving and removing KOKI flux residues—even in the tightest under-component clearances—in just 10 minutes.
The customer uses KOKI soldering paste. Its flux residues are very difficult to remove from PCBAs. Furthermore, the customer truly cares about the high quality of the production, so they tear off the components from PCBAs to be sure about the perfect cleanliness even under the components. This is a technically demanding application.
Case Study Summary (TL;DR):
We tested how to clean flux residues from PCBs after soldering process.
Type of Solder Paste:
KOKI S3X58-M500C
While standard water-based cleaning agents provide baseline flux removal, Decotron® 411A is exclusively formulated for the most technically demanding applications. It is engineered specifically to dissolve highly resistant flux residues, such as those left by KOKI S3X58-M500C solder paste, and to penetrate extreme low-standoff gaps underneath tightly spaced SMT components, ensuring flawless cleanliness where conventional fluids fail.
Decotron® 411A is a ready-mix, water-based industrial cleaning fluid (with 20% VOC content and a pH value of 11) specifically developed by DCT engineers to remove extremely resistant flux residues from Printed Circuit Board Assemblies (PCBAs) following the soldering process. Due to its exceptional ability to penetrate extreme low-standoff gaps, it provides significantly more effective cleaning under components than conventional fluids during high-pressure washing. Furthermore, this fluid is environment-friendly and completely biodegradable, meeting the strictest ecological standards for modern manufacturing.
Laboratory validation of the three-stage process demonstrated a 100% success rate in completely removing flux residues from the high-performance KOKI S3X58-M500C solder paste, provided the specified 10-minute chemical wash cycle using Decotron® 411A heated to 50 °C is strictly followed.
| Process Stage | Medium Used | Temperature | Duration | Primary Objective |
|---|---|---|---|---|
| 1. Chemical Wash | Decotron® 411A | 50 °C | 10 minutes | Active dissolution and release of resistant KOKI flux residues from the PCBA surface and under-component clearances. |
| 2. Rinse | DI Water | 25 °C | 5 minutes | Thorough wash-off of the released flux and remaining cleaning fluid from the board. |
| 3. Final Drying | Hot air | 80 °C | 10 minutes | Complete evaporation of residual moisture, ensuring absolute dryness beneath electronic components. |
The final stage of the process, drying, takes 10 minutes at 80 °C. To maximize moisture evaporation efficiency and physically remove water residues even from the hardest-to-reach places under components, InJet systems utilize the complementary AirKnife technology. This component features movable arms with nozzles that blow compressed air directly onto the board structure to remove water residue from components and connectors.
While standard water-based cleaning agents provide baseline flux removal, Decotron® 411A is exclusively formulated for the most technically demanding applications. It is engineered specifically to dissolve highly resistant flux residues, such as those left by KOKI S3X58-M500C solder paste, and to penetrate extreme low-standoff gaps underneath tightly spaced SMT components, ensuring flawless cleanliness where conventional fluids fail.
Other recommended
cleaning systems
For highly effective removal of resistant flux residues from KOKI S3X58-M500C paste, we recommend a strict three-stage cleaning protocol. It consists of an initial 10-minute chemical wash with Decotron® 411A heated to 50 °C, followed by a 5-minute rinse with deionized (DI) water at 25 °C, and concludes with a thorough 10-minute final drying with hot air at 80 °C.
This procedure is essential to overcome the strong tendency of KOKI flux residues to bake onto surfaces and embed under critical low-standoff components. While shorter times, such as a 1-minute wash, leave insufficiently cleaned areas, the described protocol ensures a 100% removal rate and guarantees the high reliability of the final electronic assemblies.
To fully utilize Decotron® 411A fluids, it is necessary to deploy vertical high-pressure Spray-In-Air systems, such as the fully automated InJet® 388 CRD 2PR or the InJet® 888 CRD.
These automated single-chamber machines ensure consistent application of the fluid with precise control of pressure and process temperature, which is recommended between 35 – 55 °C for the InJet 388 CRD 2PR. This is critical for penetrating beneath low-standoff components. To prevent cross-contamination between the washing and rinsing sections during the multi-stage process, the InJet 388 CRD 2PR features continuous 2PR filtration, utilizing a mechanical filter with a conductivity of 400 μS to remove detergent residues, followed by a final rinse using demineralized water of extreme purity (0.5 μS).
The cleaning agent should be used in systems equipped with vertical high-pressure Spray-In-Air technology, which provides the mechanical force necessary to drive the fluid under components. Recommended systems include the InJet® 388 CRD 2PR or the InJet® 888 CRD.
To ensure minimum cross-contamination between the chemical washing fluid and the subsequent rinsing stages, utilizing a machine with a unique 3-chamber layout, such as the InJet® 388 TRIPLE CRRD, is the optimal solution for maintaining process integrity.
Yes, in addition to being highly effective at removing post-soldering flux residues, this water-based cleaning fluid is also determined to clean misprints from boards prior to the reflow process, providing versatility on the SMT production line.
Because the customer uses a competitor’s cleaning system with 1 chamber only, we needed to face issues connected with high cross-contamination in this process. We managed these issues by the development of a new customized cleaning agent for this customer.
However, we would recommend implementing the cleaning system InJet® 388 TWIN CRRD in the future, which offers the minimum cross-contamination thanks to its unique 3-chamber layout.
This case study and the testing of cleaning parameters were conducted by the expert team at the DCT Czech s.r.o. laboratories. In addition to our success with KOKI paste, our laboratory has validated similar complex challenges, such as removing DowSil 4450 adhesive from stencils, eliminating Three Bond 2217H epoxy adhesives, or cleaning ALPHA CVP-390 paste residues.
For results consultation or technical support regarding the integration of InJet® systems and Decotron® fluids, you can contact our headquarters at Havlíčkova 18, 680 01 Boskovice, our billing address at Tovární 85, 679 21 Černá Hora, by phone at +420 725 337 729, or via email at info@dct.cleaning. Our cleaning systems are manufactured exclusively from stainless steel and are distributed to more than 52 countries worldwide.
